With widespread adoption of smartphones and tablet terminals in recent years, wireless traffics are sharply increasing. To address a surge in traffic, fifth-generation mobile communication systems (5G) have been studied and developed.
In a long term evolution (LTE) or LTE-advanced (LTE-A) downlink, an access scheme (orthogonal multi-access) called orthogonal frequency division multiple access (OFDMA) is used, in which many narrow-band carriers (sub-carriers) are mapped so as to be orthogonal. By contrast, as an access technique for 5G, non-orthogonal multi-access technology has been studied much. In non-orthogonal multi-access, assuming that reception process such as interference canceller at a receiver, maximum likelihood estimation, or the like is performed, a non-orthogonal signal is transmitted. As of non-orthogonal multi-accesses targeted for downlinks, downlink non-orthogonal multiple access (DL-NOMA) has been suggested (PTL 1 and PTL 2). In DL-NOMA, at a base station apparatus (also called evolved node B (eNB) or base station), modulation symbols to a plurality of different terminal apparatuses (also referred to as user equipment (UE), mobile station apparatuses, mobile stations, or terminals) are added (superposition coding) for transmission. Here, transmit power to be assigned to each modulation symbol is determined in consideration of received power (reception quality), a modulation and coding scheme (MCS: modulation scheme and coding rate), or the like at a terminal apparatus for multiplexing. Among multiplexed transmit signals, the terminal apparatus decodes a signal to another terminal apparatus, and generates a replica of the signal to the other terminal apparatus, and cancels the replica from the received signal, thereby allowing only a modulation symbol to a local terminal to be extracted.